66 lines
1.8 KiB
Go
66 lines
1.8 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package assign
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// TODO(adonovan): check also for assignments to struct fields inside
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// methods that are on T instead of *T.
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import (
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"go/ast"
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"go/token"
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"reflect"
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"golang.org/x/tools/go/analysis"
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"golang.org/x/tools/go/analysis/passes/inspect"
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"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
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"golang.org/x/tools/go/ast/inspector"
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)
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var Analyzer = &analysis.Analyzer{
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Name: "assign",
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Doc: `check for useless assignments
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This checker reports assignments of the form x = x or a[i] = a[i].
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These are almost always useless, and even when they aren't they are
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usually a mistake.`,
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Requires: []*analysis.Analyzer{inspect.Analyzer},
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Run: run,
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}
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func run(pass *analysis.Pass) (interface{}, error) {
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inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
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nodeFilter := []ast.Node{
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(*ast.AssignStmt)(nil),
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}
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inspect.Preorder(nodeFilter, func(n ast.Node) {
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stmt := n.(*ast.AssignStmt)
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if stmt.Tok != token.ASSIGN {
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return // ignore :=
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}
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if len(stmt.Lhs) != len(stmt.Rhs) {
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// If LHS and RHS have different cardinality, they can't be the same.
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return
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}
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for i, lhs := range stmt.Lhs {
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rhs := stmt.Rhs[i]
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if analysisutil.HasSideEffects(pass.TypesInfo, lhs) ||
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analysisutil.HasSideEffects(pass.TypesInfo, rhs) {
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continue // expressions may not be equal
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}
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if reflect.TypeOf(lhs) != reflect.TypeOf(rhs) {
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continue // short-circuit the heavy-weight gofmt check
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}
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le := analysisutil.Format(pass.Fset, lhs)
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re := analysisutil.Format(pass.Fset, rhs)
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if le == re {
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pass.Reportf(stmt.Pos(), "self-assignment of %s to %s", re, le)
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}
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}
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})
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return nil, nil
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}
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